1. Technical Field
The present invention generally relates to a switch mode power supply (SMPS) and method. In particular, the present invention relates to an SMPS in which data is encoded by manipulating voltage pulses on a primary side of the SMPS, and then transferred to a secondary side across a transformer.
2. Background Art
In televisions, computer monitors, and other main powered devices, off-line switch mode power supplies (SMPS) are often used to transfer power to DC-isolated outputs. A typical SMPS includes a primary side and a secondary side, which are separated by a transformer. In general, the primary side includes a main power source and a controller, while the secondary side generally includes outputs (e.g., a main load, a microprocessor), and a receiver. Due to regulations, the SMPS outputs should be isolated from the main power source (i.e., the outputs should be DC-isolated). An opto-coupler could also be provided for transferring feedback from the secondary side to the primary side. The receiver could be an IR receiver that receives a data signal from a remote control and communicates the received signal to the microprocessor for carrying out a user""s command. However, since the receiver needs to receive power at all times (even in stand-by mode), the positioning of the receiver on the secondary side requires power to be constantly transferred from the primary side. Such a configuration is highly inefficient in stand-by mode.
Heretofore, many have attempted to alleviate some of these drawbacks by including a stand-by power source controller on the primary side of the SMPS. The stand-by controller allows power to be transferred over a separate transformer solely to the microprocessor and receiver. This allows the main load output to remain off-line (i.e., without power) in stand-by mode and, thus, increases the overall efficiency of the SMPS. However, this still requires transfer of power to the receiver to occur from the primary side to the secondary side. Moreover, because an additional transformer is required, such a configuration is costly.
Another attempt to alleviate some of the drawbacks is described in U.S. Pat. No. 5,798,913 to Tiesinga et al, herein incorporated by reference. Under the configuration of Tiesinga et al., data is transferred across a transformer. However, by transferring data in the manner taught by Tiesinga et al., a linear voltage regulator is required so that the output voltages are not affected. Such a requirement is both inefficient and costly.
In view of the foregoing, there exists a need for an SMPS whereby data and power can be efficiently transferred to the secondary side without disturbing the output voltages. In addition, a need exists for such an SMPS, wherein the receiver is positioned on the primary side to obviate the need to power the receiver over the transformer. A further need exists for such an SMPS that provides adequate isolation between the outputs and the main power source.
The present invention overcomes the drawbacks of existing systems by providing an SMPS and method for transferring data across a power transformer, without affecting the output voltages. In general, the SMPS and method of the present invention encodes data by manipulating pulses generated on the primary side. The encoded data is then transferred to the secondary side, over the transformer, where secondary side pulses containing the encoded data are generated in response to the primary side pulses. The secondary side pulses are then sensed and decoded.
According to a first aspect of the present invention, a switch mode power supply (SMPS) having a primary side and a secondary side separated by a transformer are provided. The SMPS comprises: (1) a controller that regulates the generation of pulses on the primary side; and (2) an encoding system for encoding data by changing a frequency of a set of the pulses on the primary side.
According to a second aspect of the present invention, a switch mode power supply (SMPS) is provided. The SMPS comprises: (1) a primary side including a main power source, a controller, and a receiver, wherein the controller regulates the generation of pulses on the primary side and encodes data by changing a pulse width for a set of the pulses; (2) a secondary side for receiving power and the encoded data from the primary side, wherein the secondary side includes a main load, a microprocessor, and a detector, and wherein the detector senses the encoded data by detecting manipulations in secondary side pulses generated in response to the primary side pulses; and (3) a transformer separating the primary side from the secondary side.
According to a third aspect of the present invention, a method for transferring data from a primary side to a secondary side of a switch mode power supply (SMPS) is provided. The method comprising the steps of: (1) changing a width of pulses on the primary side to encode data; (2) transferring the encoded data to the secondary side; (3) sensing the encoded data on the secondary side; and (4) decoding the encoded data.
Therefore, the present invention provides an SMPS and method. The present invention reduces the problems associated with existing systems set forth above.